The following computer-generated description may contain errors and does not represent the quality of the book:The author would like to apologize for the delay in acknowledging requests for advance copies of this paper. In addition to a nominal clerical delay resulting from normal overloads at the beginning of an academic year, Section 3 of the original draft was substantially revised and extended at the suggestion of some colleagues at M.I.T.

The research reported herein is one part of a larger program currently in progress. Any comments or criticism relating to this research would be most welcome.